[JDUBS]

Hey Guys

I've seen it mentioned both ways before - but, definitively(?), does a big (say 3kva) isolation transformer provide a lower output impedance than plugging directly into the wall?  Or not?

If not, how can you get to a lower output impedance than the wall and INCREASE dynamics for power hungry equipment?  I think PS Audio touts certain of their products as being better (from an impedance perspective) than plugging directly into the wall.

Thanks all!

Jim

[G Georgopoulos]

the bigger the transformer the lower the impendance,mains transformers are bigger than 3kw so mains has lower impendance,kindergarden stuff really...

[brj]

Possibly of interest:

http://www.audiocircle.com/index.php?topic=96288

Doesn't go into great detail, but the link in the OP's post leads you to related material.

[Pete Schumacher]

Hey Guys

I've seen it mentioned both ways before - but, definitively(?), does a big (say 3kva) isolation transformer provide a lower output impedance than plugging directly into the wall?  Or not?

If not, how can you get to a lower output impedance than the wall and INCREASE dynamics for power hungry equipment?  I think PS Audio touts certain of their products as being better (from an impedance perspective) than plugging directly into the wall.

Thanks all!

Jim

If the transformer steps down the voltage a little, it will also lower the impedance, a little. 

If it's a 1:1 transformer, regardless its rating, it will have a higher output impedance than plugging directly into the wall.

If you have an active system, one that stores power and then provides a regulated output, then you could be providing a lower output impedance.

[Speedskater]

Unless the transformer is a 240V to 120V unit, no it won't lower the AC power line source impedance.
About a year and a half ago, I said that I would write a short note about anyone could safely measuring their 'AC power line source impedance' at the point of use. So that you could see what the power conditioner was really doing.
I'll skip over questions about just how audible a high impedance might be.

[JDUBS]

Possibly of interest:

http://www.audiocircle.com/index.php?topic=96288

Doesn't go into great detail, but the link in the OP's post leads you to related material.

YES!  This is exactly what I was talking about - thank you!

How can you get lower output impedance (vs. the wall) and ALSO not constrict dynamics?!  Is it possible?

-Jim

[ACHiPo]

the bigger the transformer the lower the impendance,mains transformers are bigger than 3kw so mains has lower impendance,kindergarden stuff really...

Wow G, you took electronics in kindergarten? 

[randytsuch]

This was written in for tube output transformers
http://www.diyaudio.com/forums/tubes-valves/125007-output-transformer-impedance-question.html

But a transformer is a transformer, so I would think that the actual output impedance depends on the turns ratio and the input impedance to the transformer.

So theoretically, a 1:1 transformer doesn't effect output impedance.

In real life, I expect the wire gauge and the transformer core would effect the ability of the transformer to respond to changes in demand for current, which would show up as a loss in dynamics.

Randy

[Speedskater]

The output power of a transformer is always slightly smaller than the input power. Because all transformers have small losses.
A transformer allows you to increase the output voltage while decreasing the output current or:
decrease the output voltage while increasing the output current.
There is no free lunch with transformers.

[G Georgopoulos]

Unless the transformer is a 240V to 120V unit, no it won't lower the AC power line source impedance.

Agreed,that's what i was refering to, the power company stepdown transformers,also an 1:1 transformer with bigger power rating has lower impendance compared to another smaller 1:1,cheers...

[Speedskater]

Power company step-down transformers, are 4000V or maybe 12,000V down to 240V transformers. Something like 25:1 or 50:1.
But a transformer all by itself can't be viewed as having a source impedance. You have to look at the entire primary circuit.

[jea48]

Hey Guys

I've seen it mentioned both ways before - but, definitively(?), does a big (say 3kva) isolation transformer provide a lower output impedance than plugging directly into the wall?  Or not?

If not, how can you get to a lower output impedance than the wall and INCREASE dynamics for power hungry equipment?  I think PS Audio touts certain of their products as being better (from an impedance perspective) than plugging directly into the wall.

Thanks all!

Jim

I think you might be confusing the impedance, measured in a percentage, to the proper sizing of an isolation transformer and the size of the feeder, conductors, feeding the primary of the transformer for a specified connected load to the secondary of the transformer.

For your example you used a 3KVA transformer. First off a 3KVA transformer is big if you are using it to power a preamp or a CDP or both.  On the other it is not big if you are going to feed an entire audio system with a decent sized power amplifier.

I can't count the number times where I have read somebody is using a 120V to 120V isolation transformer that is sized bigger than the wiring used to feed the primary of the transformer.
 Just for an example, a 120V to 120V 3KVA transformer that is plugged into a 15 amp convenience outlet branch circuit will not supply any more current  to a connected load than the 120V 15 amp convenience branch circuit can supply.

If the connected load on the 120V 15 amp branch circuit was causing VD, voltage drop, or in the case of a connected power amplifier causing fluctuating VD caused by the amplifier being driven hard playing dynamic music through it, the output of the 3KVA transformer will reflect what's happening on the mains feeding the transformer.
 

[werd]

I think you might be confusing the impedance, measured in a percentage, to the proper sizing of an isolation transformer and the size of the feeder, conductors, feeding the primary of the transformer for a specified connected load to the secondary of the transformer.

For your example you used a 3KVA transformer. First off a 3KVA transformer is big if you are using it to power a preamp or a CDP or both.  On the other it is not big if you are going to feed an entire audio system with a decent sized power amplifier.

I can't count the number times where I have read somebody is using a 120V to 120V isolation transformer that is sized bigger than the wiring used to feed the primary of the transformer.
 Just for an example, a 120V to 120V 3KVA transformer that is plugged into a 15 amp convenience outlet branch circuit will not supply any more current  to a connected load than the 120V 15 amp convenience branch circuit can supply.

If the connected load on the 120V 15 amp branch circuit was causing VD, voltage drop, or in the case of a connected power amplifier causing fluctuating VD caused by the amplifier being driven hard playing dynamic music through it, the output of the 3KVA transformer will reflect what's happening on the mains feeding the transformer.
 

With my 3KVA Torus 240V you can drive about 300 watts of SS power effectively including the rest of the gear. This is a 120v 20 amp outlet.  Anything more and the amp transformer is too big and sits too close to the Isolation transformer.  All the big amps I have had it starts generating a bit too much treble glare with no apparent gain in dynamics. The wall is the best place for big amps. With the amp transformer seeing nothing more than an outlet, a fuse box and then the local transformer. Hopefully the local neighborhood transformer isn't too far away. Like sitting on a pole in your back yard feeding your house and the rest of the neighborhood is best.